Re: [SMS D-Bus 02/19] sms: introduce message ID API
Hi Inaky,
> The current message id is 32 bits. Why are we stopping at 16?
We could
> go all the way to 64 if needed...
Well, at the end what gets sent to the network is 16 bits right?
So I think we're all confused here. This ID is not being sent to the
network. It is only used for uniquely identifying the message over
D-Bus and to message history. This number can be as small or as big as
we want.
> Also, we need to take time and some random value into account. Perhaps
> including time() output and a simple static counter into the hashing
> function would make it unique for those 'same sender, same contents
> messages'
So then we really don't care about being able to regenerate the hash ID
from the contents?
The design discussions we held about this involved being able to, with
the content of the message and destination number, generating a hash
that could be uniquely reproduced by rehashing it again. You had a
reason for it and I can't remember which one it was -- I should have
written it down. But that brought the problem of 'somebody sending the
same message to the same number' which yields the same ID.
However, if to fix that we are adding randomness in the form of time(),
why bother with the contents? let's just do a random ID from the ground
up and save us the pain of hashing.
I don't remember this discussion any more. There might be a case where
an old message is re-delivered because oFono crashed after delivery but
before deletion.
At least to me it seems that generating a random int is really not
guaranteed to be unique over reboots. Hashing seems way better.
However, I'm not a math/crypto geek, so feel free to prove me wrong.
Regards,
-Denis